For years I have put up with TopStyle freezing after many iterations of going back and forth between the Editor and viewing the results in a browser. It does not matter which browser; it will eventually freeze up when attempting to invoke the browser. The number of times the browser is called before a freeze-up will vary.
I always assumed this bug would eventually be fixed. Now, looking at the bug reports, I am not sure. Something about the TopStyle program's memory management may be fundamentally incorrect.